A semiconductor light emitting device includes a body of semiconductor material, generally composed of group III-IV compounds, having a thin active layer with a layer of p-type conductivity material on one side of the active layer and a layer of n-type conductivity material on the other side of the active layer. Such a laser typically emits light in more than one optical mode which limits its utility. Botez, in U.S. Pat. No. 4,215,319 issued July 29, 1980, and entitled SINGLE FILAMENT SEMICONDUCTOR LASER and assigned to the assignee of the present application, has disclosed a semiconductor laser having a stable, single mode output light beam. The control over the output light beam in this laser arises from the tapering in thickness of the layers prepared by deposition of the confinement and active layers onto a substrate having a pair of substantially parallel grooves therein. The tapering is caused by the difference in growth rate of the layers over a land between the grooves and over the grooves when the layers are prepared by liquid or vapor phase epitaxy.
However, if the layers are deposited on an InP substrate having such a pair of parallel grooves using either liquid or vapor phase epitaxy, flat, planar surfaces are observed with the layer growing faster over the grooves than over the flat substrate portions so as to form a continuous, smooth surface. This growth habit of InP limits the utilization of the structure disclosed by Botez for light emitting devices of InP and related alloys. It would be desirable to have a light emitting device composed of InP and related alloys which exhibits an output light beam of comparable quality to that produced by the device of Botez.